I'm coming up 63 y/o.
I've got a light weight Carrera Cross city , a Mycle Ebike Climber and and Engwe, all good fun and capable of what they were designed for.
I've got a Halfords Crosscity folding E-bike, it's ace, it'll tackle most hills, folds up quite compact and will do between 14 to 21 miles on a charge dependent on terrain.
I have a Carrera Crosscity folding ebike , it's ace, tackles most hills, folds down to fit in a car boot and around 18 miles range if taking it steady in a hilly area .
Hi, I'm from Teesside area too.
That bike should be OK to convert.
I'd recommend going with a 48 volt system,
Front wheel is easier to do, but back wheel is better.